Electrochemical Degradation of Naproxen (NPX) and Diclofenac (DFC) through Active Chlorine Species (Cl2-active): Considerations on Structural Aspects and Degradation in Urine

Abstract

The electrochemical degradation of two highly consumed analgesics, naproxen (NPX) and diclofenac (DFC), mediated by chloride ions and using a dimensionally stable anode (Ti/IrO2), is compared. In the first part, the ability of the system to generate reactive chlorine species was evaluated as a function of the current density (j= 1.25, 3.13, 5.00 mA cm-2) and the chloride concentration ([NaCl]= 0.01, 0.025, 0.05 mol L-1). Subsequently, under proper conditions, the process performance to degrade the pharmaceuticals individually and mixed, in distilled water and synthetic fresh urine, was evaluated. The electrochemical system achieved 100 % of NPX and DFC elimination in distilled water at 0.017 and 0.056 Ah L-1, respectively. A strong dependence on the chemical structure of the analgesic was evidenced in the degradation kinetics. Finally, slow elimination of the pharmaceuticals in the urine was observed, because of compounds in this complex matrix that compete for the degrading agents.